Archive same email to many cases but email gone from old to new (outlook plug-in)

I have some situation that user want to archive same email with attachments to 2 cases via outlook plugin but when I archive email to create a new case, Email will gone form old case then appear to new case. So I check in a relationship between email and old case it has been deleted, seems like same email not allow to create more than one case.

Is it normal situation or not ?

Moreover user said that its working before, after we change email server to Office365 seem to have a problem.